"I was nervous the first couple of matches, and for some reason, this match I kind of felt at home," Fox said. "I was finally playing with the galleries and enjoyed myself out there, and really just had fun."

The 21-year-old Fox, from Hendersonville, Tenn., beat the 21-year-old Williams, from Moscow, Idaho, 4 and 2. A senior at the Tennessee-Chattanooga, Fox will play Brandon Hagy of Westlake Village, Calif., in the semifinals Saturday. The 21-year-old Hagy, one of two golfers from the University of California to reach the semifinals, beat Cheng-Tsung Pan of Taiwan 4 and 3.

Michael Weaver of Fresno, Calif., who also a member of Cal's golf team, beat Ricardo Gouveia of Portugal 4 and 3. He'll meet Alabama's Justin Thomas of Goshen, Ky., in the other semifinal. Thomas edged Australian Oliver Goss 2-up.

Fox made two birdies in a bogey-free front nine. Williams had two bogeys.

"This is by far the best thing I've done in my career, by far," Fox said.

"I knew I had to play well and had to bring my `A' game, and luckily I did," said Fox, who advanced to match play after winning a playoff in stroke-play qualifying. "But we started out and I got 2-up through four, and to be 4-up after nine was beyond expectations. I thought it was going to be a really close match. I give him respect for being the No. 1 amateur, but luckily I got it done."

Like Fox, Weaver parlayed a strong start into a victory over Gouveia, who hadn't trailed in any of his matches before the quarterfinals.

Weaver was up by two holes after five and stretched his advantage to 4-up after nine.

He failed to advance to match play in last year when he missed the cut by a stroke and had to survive a playoff just to get into match play this year.

"I'm having a great week. Couldn't be happier," Weaver said. "Just to make it through the playoff was great. I feel like I've played smart and I've put myself in a great position."

The 19-year-old Thomas, 19, the Jack Nicklaus Award winner as the nation's top collegiate player, was only 1-up on Goss heading into No. 18. Thomas was able to make par and the 18-year-old Goss, an incoming freshman at Tennessee, missed a long putt from the lip of the green to try to square the match.

"It was a hard match," Thomas said. "You're obviously not going to get any easy matches at this point. It feels great to be moving on and I'm very, very honored."

Hagy birdied the seventh hole to take his first lead. He stretched his lead to 2-up when Pan, who plays for Washington, bogeyed No. 10.

"I think that stretch right there ... was huge," Hagy said. "Then I birdied the next hole to go 1-up. That was a huge swing. I played really consistent the whole rest of the way."